1. Field of the Invention
The present invention relates to the technical field of display panels and, more particularly, to a pixel data conversion method and apparatus for display with delta panel arrangement.
2. Description of Related Art
Current consumer electronics or handheld devices are typically equipped with a liquid crystal display (LCD) panel as a human-machine interface for providing convenient viewing to a user. Generally, the LCD panels include two types, strip panels and delta panels. The strip panel is typically a large panel used in a notebook, for example. FIG. 1 is a schematic diagram of a typical strip panel. On the strip panel 100, each pixel 110, 120 has a red subpixel R, a green subpixel G, and a blue subpixel B, and the three color subpixels of each pixel generate a different brightness respectively, for being mixed into various colors.
The strip panel 100 includes multiple horizontal lines, and a display controller (not shown) provides color data to the red, green, blue subpixels R, G, B of each pixel, respectively. When the strip panel 100 has a resolution of 720×480, it indicates that the strip panel 100 has 480 horizontal lines having 720 pixels respectively, where a pixel has three color subpixels, i.e., red, green, and blue subpixels.
The strip panel 100 is based on the control of the pixel clock to concurrently receive the color data for updating the red, green, blue subpixels of a special pixel each time and further displaying different brightness respectively, so as to mix them into various colors. When all pixels of the panel are updated by controlling the scan lines in one-by-one manner, a complete frame is shown on the strip panel 100.
FIG. 2 is a timing diagram of color data and pixel clock for the strip panel 100 of FIG. 1. When an external video signal (such as an analog or digital TV video signal) is displayed by the strip panel 100, the image processing circuit (not shown) processes and samples the external video signal and further generates a pixel clock, a red data, a green data, a blue data. The red data, the green data, and the blue data are outputted by a red data line, a green data line, and a blue data line of the image processing circuit, respectively. The data sizes of the red, green, blue data can indicate a brightness of color unit respectively. Namely, the red, green, blue data corresponding to the rising edge of the first pixel clock can drive the three color subpixels of the first pixel, and the red, green, blue data corresponding to the rising edge of the second pixel clock can drive the three color subpixels of the second pixel, and so on. For an example of the strip panel 100 with a resolution of 720×480, the red, green, blue data corresponding to the first 720 pixels indicate the color data corresponding to the three color subpixels in all pixels of the first horizontal line. Similarly, after the 720×480 pixel clocks, the color units in all pixels of the entire strip panel 100 can receive a color data respectively, so the update is completed so as to display a complete image on the panel.
A small panel (such as a car display panel, a display panel used in a camera) uses a delta panel. FIG. 3 is a schematic diagram of a typical delta panel 300. For a delta panel 300, each pixel 310, 320, 330 has only one color pixel, which is surrounded by the other two color pixels, and the horizontal lines are arranged in interlacing to one another. The three color units (as indicated by a triangle in FIG. 3) consisting of a combination of three pixels generate different brightness respectively for being mixed into various colors.
When the delta panel 300 has a resolution of 320×480, also written as 320RGB×480, it indicates that the delta panel 300 has 480 horizontal lines having 960 pixels respectively. A sequence of red pixel R, green pixel G, and blue pixel B is repeatedly arranged for an odd-numbered horizontal line, and a sequence of green pixel G, blue pixel B, and red pixel R is repeatedly arranged for an even-numbered horizontal line. The position of each pixel in an even-numbered line has a half-pixel dislocation to the position of each pixel in an odd-numbered horizontal line.
If the strip panel 100 of FIG. 1 has an image to be displayed with a resolution of M×N as same as the delta panel 300 of FIG. 3, the data line signal and pixel clock generated by the image processing circuit, as shown in FIG. 2, are not suitable for the delta panel 300 of FIG. 3. Thus, a complicated control circuit has to be added between the typical image processing circuit and the delta panel 300 of FIG. 3 in order to appropriately convert the color data and pixel clock generated by the image processing circuit before sending to the delta panel 300.
According to the specification of the delta panel 300, each color unit has a respective color clock and color data line, i.e., a red clock Clk—3/R and red data line, a green clock Clk—1/G and green data line, and a blue clock Clk—2/B and blue data line. FIG. 4 is a timing diagram of color data of data lines and associated pixel clocks that are converted by a typical control circuit. Generally, the typical control circuit has a clock generator to process the pixel clock and further generate color clocks with one third of a frequency of the pixel clock that includes a red clock, a green clock, and a blue clock. As depicted in the red data, green data, blue data of FIG. 4, only one third of the M×N color data is selected and displayed. Namely, as shown in FIG. 4, the first, fourth, seventh, and tenth red data are displayed, and the time of three pixel clocks is maintained.
By comparing FIG. 2 with FIG. 4, it is known that the first RGB data is displayed, and the second RGB data and the third RGB data are not outputted for display. Similarly, the fourth, the seventh, the tenth RGB data are outputted for display, and the other RGB data are not outputted for display. When the three color clocks are at the rising edges (indicated by the arrows), the corresponding red data, green data, and blue data are displayed on the panel.
Taking the first row of pixels as an example. In the previous M pixel clocks, the rising edge of the first red clock is synchronous with the first pixel clock in order to present the first color data of the red data line at the position of the first pixel. Similarly, the rising edge of the first green clock is synchronous with the second pixel clock in order to present the first color data of the green data line at the position of the second pixel, the rising edge of the first blue clock is synchronous with the third pixel clock in order to present the first color data of the blue data line at the position of the third pixel, and so on. After the M×N pixel clocks are generated, a complete image is displayed on the entire delta panel 300.
Obviously, the typical control circuit reduces the desired resolution after the signal conversion. For example, the delta panel 300 has a resolution of M×N as same as the strip panel 100, but its actually present resolution is only one third of the strip panel. That is, some details of the desired image cannot be completely present due to the resolution reduction.
For such a problem cited above, Hung; Jui-Hung, in US Patent Publication No. 2007/0229422, described a clock duplicating circuit for receiving a pixel clock outputted by an image processing circuit to thereby generate three color clocks with a frequency of one third of the pixel clock, and the three color clocks have a duty cycle of 50% . In this case, a clock adjusting device is used to receive the three clocks generated by the clock duplicating circuit in order to adjust each of the three clocks, so that there is a phase difference of 120 degrees between every two of the clocks, and then the three adjusted clocks, i.e., a green clock Clk—1/G, a blue clock Clk—2/B, and a red clock Clk—3/R, are outputted. The color data line 31 of the image processing circuit directly acts as the color data (i.e., green, blue, red data) on the horizontal lines of the delta panel for improving the frame quality. FIG. 5 is a timing diagram of color data and associated pixel clocks for horizontal lines of a typical delta panel disclosed in the US Patent Publication No. 2007/0229422. FIG. 6 schematically illustrates a relationship of three color subpixels of the strip panel and pixels of the delta panel. As shown in the description of FIGS. 5 and 6, the color data of the strip panel 100 directly acts as the color data (i.e., green, blue, red data) of scan or horizontal lines of the delta panel 300. Namely, one of the three color subpixels at the position of a pixel of the strip panel is extracted and displayed as a pixel of the delta panel at the same position. However, such a conventional pixel data conversion does not consider that the position of each pixel in an even-numbered horizontal line has a half-pixel dislocation to the position of each pixel in an odd-numbered horizontal line, resulting in that the defects of zigzag edges, line deformation, or color fringing typically present in displaying on the delta panel. Therefore, it is desirable to provide an improved pixel data conversion to mitigate and/or obviate the aforementioned problems.